Dispensing devices requiring mixing of at least two substances prior to dispensing are known in the art. These devices dispense a variety of pasty or highly viscious products including adhesives, joint fillers, foams, sealants, grouts, molding compounds, etc. The dispensed products are typically formed by mixing at least two previously separated substances to form a reaction product which is then dispensed from the device. The respective substances may be passed or pushed through a static mixer located within the device to facilitate mixing and thereby reaction. The reaction product is then dispensed through the dispensing end of the device to accomplish a desired application.
Typical of such prior art devices is that illustrated in U.S. Pat. No. 5,333,760. This patent discloses a cartridge mixing and dispensing device that is widely used. However, this device is not suitable for use when high-pressure build-up and pressure backflow occurs in the device due to gas generation during the reaction of the respective substances. Such build-up and backflow may result in bending or other types of damage to the dispensing device.
When a desired dispensing application requires the use of a reaction product that is produced by a reaction that creates high pressures in the device, i.e., on the order of 45 psi or higher, the device may be damaged. Pressure build-up occurs once the reaction product commences exit from the device because the product exit seals the dispensing means or exit orifice. Such pressure build-up can then result in undesirable pressure backflow into the feeding system of the dispensing device once feeding ceases. The present invention solves the above problem in an efficient and effective manner by providing a check valve at the end of the mixing and reaction chamber opposite the dispensing end of the chamber. A check valve affords a convenient mode of preventing back pressure that could damage the feeding system of the device.
U.S. Pat. No. 6,241,125 discloses an overall system of variable connections for the application of several materials. A check valve is indicated in FIG. 3 of the patent as a component of the packer assembly. Such check valves are common for such assemblies. However, no check valve is used within the mixing and reaction portion of the assembly.
U.S. Pat. No. 5,477,987 illustrates a pump system that incorporates check valves in its output side. These valves function to prevent the respective materials from cross contamination. Again, such check valves are not associated with the mixing and reaction portion of the device.